Progresele înregistrate în procesul de obținere a foilor de nanotuburi de carbon în masă(Progress achieved towards mass producing carbon nanotube sheets)

CNT-urile sunt foi de carbon care au fost laminate în tuburi, măsurând 100.000 de ori mai mici decât diametrul părului uman. Proprietățile lor electrice, chimice, termice și mecanice excepționale le fac un material ideal pentru nenumărate aplicații, inclusiv pentru stocarea energiei, cipuri de calculator și senzori. Potențialul revoluționar al CNT-urilor în ingineria materialelor se reflectă în creșterea prognozată a valorii de piață, care se așteaptă să ajungă la 8,7 miliarde de dolari până în 2022, potrivit analistilor de piață Markets and Markets. Buckypaper este o foaie subțire din nanotuburi de carbon agregate.

Posted: Sep 27, 2017
Progress achieved towards mass producing carbon nanotube sheets (Nanowerk News) Researchers at the Masdar Institute have recently announced a breakthrough approach to producing carbon nanotube (CNT) sheets, known as ‘buckypaper,’ through a scalable, low-cost and simple technique. The novel fabrication method could help bring game-changing buckypaper applications a step closer towards cost-effective commercialization.
“Being able to produce buckypaper in a scalable way like this has not been demonstrated before. This new technique could boost the development of market-ready applications, including high-power lithium-ion batteries and low-cost vanadium-redox-flow batteries,” said Dr. Rahmat Susantyoko, postdoctoral researcher from the Mechanical Engineering Department.
Dr. Susantyoko was first author of a paper that describes the new technique, called Surface-Engineered Tape-Cast (SETC), which was published last month in the Journal of Materials Chemistry A („A surface-engineered tape-casting fabrication technique toward the commercialisation of freestanding carbon nanotube sheets”).

Buckypaper
CNTs are sheets of carbon that have been rolled into tubes, measuring 100,000 times smaller than the diameter of human hair. Their exceptional electrical, chemical, thermal and mechanical properties make them an ideal material for countless applications, including in energy storage, computer chips, and sensors. The revolutionary potential of CNTs in materials engineering is reflected by the projected growth of its market value, which is expected to reach US$8.7 billion by 2022, according to market analysts Markets and Markets. Buckypaper is a thin sheet made of aggregated carbon nanotubes.
Despite the technical potential of buckypaper, a critical problem continues to hinder its development for CNT applications. The difficulty of converting CNTs from their original fine, dust-like powdery state, to a solid, thin film of grouped CNTs remains a key challenge.
CNTs in buckypaper form are much easier for engineers to manipulate. In their macroscopic manifestation, CNTs can be processed and developed into useful materials for a broader range of applications. While many innovative buckypaper-based applications have been developed in recent years, they failed to achieve broad commercialization because they lacked a scalable and cost-effective buckypaper fabrication process.
“Common buckypaper fabrication methods used today are membrane filtration and chemical vapor deposition. However both methods have severe limitations, with membrane filtration restricting the size of the produced buckypaper to the size of the membrane and apparatus used, and chemical vapor deposition being exceedingly expensive,” Dr. Susantyoko explained.
Addressing the need for a low-cost, scalable fabrication method, Masdar Institute’s SETC technique offers a novel solution that leverages tape-casting – a method traditionally used to coat a CNT film over a substrate – that overcomes the current technological limitations that have prevented low-cost, scalable buckypaper fabrication till now.
“Our technique utilizes tape-casting with a special type of substrate, which we engineered in the lab, that allows us to easily peel off the buckypaper from the supporting substrate, resulting in a free-standing buckypaper film,” Dr. Susantyoko said.
Identifying the ideal substrate that would allow the buckypaper to easily peel off was the biggest challenge. Through investigation, the team discovered that buckypaper sticks to smooth and randomly-patterned rough surfaces, but separates from a special kind of surface that has a rough structure composed of micro-sized pyramids.
“We realized that the surface morphology of substrate and dissimilarity in surface energy of CNT–substrate play important roles in affecting the ability to easily peel off the CNT film,” Dr. Susantyoko added. He explained that the unique morphology and high surface area created by the micro-pyramids enabled the easy separation of the CNT sheet.
To demonstrate the effectiveness of their SETC buckypaper fabrication technique, the team used it to produce a buckypaper-based cathode for a high-power lithium-ion battery. Now, the team is enhancing their SETC method to produce an even higher-powered cathode, which is intended to be used for space applications.
By providing materials scientists with a scalable, low-cost and simple method to fabricate CNT sheets, Masdar Institute researchers are helping to bring the game-changing CNT innovations being developed in labs across the world to the market.

Scrierea nanotuburilor cu un stilou injector nano

echipa a dezvoltat un nanopen simplu pentru desenarea și plasarea nanometrică a moleculelor singulare sau multiple, cum ar fi tijele. Acest lucru este exemplificat în lucrare printr-un accent pe nanotuburile de carbon, considerat pe scară largă ca un element critic în electronica moleculară.

Posted: Mar 02, 2016

Writing nanotubes with a nano fountain pen

(Nanowerk Spotlight) One of the fundamental challenges in the development of nanoelectromechanical systems (NEMS) – and of nanotube- and nanowire-based devices in general – is the large-scale controlled placement of molecular sized building blocks on a substrate.The ability to effectively place at will molecules so that they can be rapidly organized into functional components is a core requirement of many nanotechnology applications, components and functional devices.In new work, an international team of researchers describes the drawing and Raman characterization procedure developed for placing single-walled carbon nanotubes (SWCNTs), proof of SWCNT alignment, optimization of the drawing parameters, and the subsequent placement in predefined lithographic structures for the demonstration of electrical conductivity.The findings have been published in the January 20, 2016 online edition of Nano Letters („Nanodrawing of Aligned Single Carbon Nanotubes with a Nanopen”).In essence, the team developed a simple nanopen for drawing and placing aligned single or multiple rod like molecules nanometrically. This is exemplified in the paper by a focus on carbon nanotubes, considered widely as a critical element in molecular electronics.Controlled direct drawing of SWCNTs on SiO2. (a) A diagrammatic representation of the drawing process. The SWCNT alignment occurs by capillary forces in the direction of drawing. (b) Raman mapping of the written structure of the G+ band together with (c) a Raman spectrum at a point in this image. (d) AFM of the written structure before washing with (e) a line scan of a particular location. The height of the drawing is 200-250 nm, and the line width is 600-800 nm. (f) AFM of a portion of the written structure that has been washed after 4 days of drying, with (g) a line scan at a particular location. After washing only the SWCNTs remained on the substrate with the associated surfactant and solution being washed away. The height of the drawn structure is between 0.8 and 2.9 nm. (Reprinted with permission by American Chemical Society)”The basis of the methodology, which is the use of capillary forces during nanowriting of chemicals, should have general applicability in many areas such as polymer molecules, DNA where molecular placement is fundamentally and technologically of considerable import, nanoparticle manometric deposition, the deposition of metallic lines etc.,” Aaron Lewis, a professor at The Hebrew University of Jerusalem, Israel, tells Nanowerk.Thus, from the point of view of the paper, it is now feasible to write molecular components into circuit functionalities. As Mark Ratner from Northwestern commented a few years ago: „Connecting molecular nanowires in a controlled fashion to single molecules that function like circuit elements is one of the great challenges of the field (of molecular electronics).””The fundamental implications of our work is that we present a general method of chemical nanowriting that is applicable to any surface hydrophobic or hydrophilic, rough or smooth, with liquid or with gases,” Lewis points out.The team’s fountain pen nanolithography (FPN) method uses a simple glass cantilever as a nanofountain pen to draw a carbon nanotube solution directly onto a substrate with atomic force feedback.The SWCNTs are deposited and aligned by capillary forces in the drawing direction at a speed of microns per second.”FPN has overtones of the dip pen nanolithography (DPN) method but has some powerful advantages,” explains Lewis. „FPN does not have DPNs preference for hydrophilic substrates like gold and does not need to deposit linker molecules for deposition of SWCNTs as is the case in DPN. In addition, the nanopens used in FPN are optically transparent and have their drawing tip highly exposed to the optical axis for accurate placement within a device structure.”Potential application areas for FPN are molecular circuit design; mask repair at the highest of resolutions by either adding or removing with a solvent and the nanopen errors in the mask; flat panel display repair of electronic components with molecular of nanoparticle inks; placement of structured defects in photonic band gap or plasmonic optical components for guiding light in specific directions more effectively.The team is planning to demonstrate the broadened scope of this method for many different directions in science and technology.”Basically, what we have shown for carbon nanotubes now needs to be applied to other molecular systems,” says Lewis. „However, not only in terms of writing recipes for these systems on any surface but characterizing such things as the ability to write on a structure already previously drawn by the Nanopen. This among many other features is unique to this method.”By Michael Berger – Michael is author of two books by the Royal Society of Chemistry: Nano-Society: Pushing the Boundaries of Technology and Nanotechnology: The Future is Tiny. Copyright © Nanowerk